Project Summary/Abstract The current proposal represents a combined clinical human and experimental animal model investigation which seeks to examine obesity-associated metabolic and vascular disease mechanisms. Obesity has developed into one of our most critical health care problems as 69% of the US population is currently overweight or obese. Adipose tissue dysfunction, lipotoxicity, and insulin resistance are essential abnormalities linking obesity to the pathogenesis of cardiovascular disease. This proposal will employ a number of complementary approaches harnessing physiological studies of vascular endothelial vasodilator function and angiogenesis in live vessels, innovative cell-autonomous gain-and- loss of function biological methods, and animal model constructs to gain novel insight into the role of a newly identified protein FSP27 in the pathogenesis of vascular disease. In aim 1, we will investigate the role of FSP27 in depot-specific mechanisms of arteriolar dysfunction in the human adipose tissue microenvironment, using videomicroscopy and angiogenic assays to examine microvascular responses in both subcutaneous and visceral adipose compartments biopsied during elective surgical procedures, in 100 obese and 25 lean subjects. We will test the hypothesis that down-regulation of FSP27 is linked to insulin resistance and vascular dysfunction, and also seek evidence that FSP27 overexpression using a novel adenoviral approach reverses obesity-related vascular dysfunction. In aim 2, we will probe mechanisms of FSP27 action and identify regulatory molecular pathways that define endothelial phenotypes by conducting cell-line specific gain-and-loss of function studies in primary human cells derived from aim 1. We will also seek to characterize the relative contribution of adipocyte vs. endothelial cell FSP27 expression in the control of vascular phenotype, and will test our hypothesis that adipose-endothelial cross-talk plays a crucial role in the regulation of vascular dysfunction. In aim 3, we will utilize innovative mouse models that are engineered to over-express endothelium- and/or adipocyte- specific human FSP27 to seek evidence for a protective effect of FSP27 against vascular dysfunction. The overall project will use major strengths of two laboratories with cardiovascular (Dr. Gokce) and adipocyte biology (Dr. Puri) expertise, and combine molecular biology with human physiology in severely obese individuals where clinically very little vascular data currently exist. Our proposal may unravel novel pathways along the adipocyte-endothelial axis that act as critical modulators of vascular biology and potentially lead to the identification of new drugable targets and approaches to reverse obesity-induced cardio-metabolic disease.